This invention relates to a carbon containing refractory for use in a molten metal refining furnace, superior in resistance to thermal shock and corrosion, and durable during use under severe conditions.
Recently, carbon containing refractories are increasingly used as a refractory for a molten metal refining furnace in order to prevent permeation of molten metal and/or slag into the refractory body or to make the refractory body high-heat-conductive and low-expansible to improve the resistace to thermal shock. Generally, carbon containing refractories are formed as various combinations of carbon and refractory oxide aggregate, such as alumina-carbon, magnesia-carbon, zirconia-carbon, and so on, according to the conditions under which the refractory is used, including the type of furnace and the slag composition.
In more detail, if the proportion of carbon is increased in the refractory oxide aggregate-carbon composition, the heat conductivity becomes higher and the thermal expansion coefficient becomes smaller, thereby improving the resistance to thermal shock as well as the anti-slag-permeation properties. In this case, however, the resistance to corrosion becomes lower since the content of the high-corrosion-resistant oxide aggregate is relatively reduced. If, conversely, the proportion of oxide aggregate is increased, the resistance to corrosion is improved but the heat conductivity becomes lower and the thermal expansion coefficient becomes higher, since the proportion of carbon becomes relatively small, resulting in a reduction in the resistance to thermal shock as well as a deterioration in the anti-slag-permeation properties.
Under the present conditions, in the carbon containing refractory based on combinations of refractory oxide aggregate and carbon, the contents of respective components are restricted within suitable ranges according to the conditions under which the refractory is used, in order to balance the resistance to thermal shock, the anti-slag-permeation properties and the anti-corrosion properties with each other.